So from what I can tell there appear to be a "narrow" and a "wide" version of the chrome trim on the top of the doors.
Does anyone know what this chrome trim is called and if / where it can be purchased?
The one you are calling "narrow" is not a trim piece, it is actually part of the side glass seal/weather strip available at most of the resto suppliers. The wide trim piece was offered as an optional item and I don't believe it is reproduced by anyone.